1. Field of the Invention
The invention relates to communicating information using digital watermarks.
2. Description of the Related Art
The technique of marking paper with a watermark for identification is as almost as old as papermaking itself. With the advent of digital media there are many techniques for applying this ancient art to our new technologies. Such a watermark, applied to digital media, is referred to as a digital watermark. A digital watermark is described by M. Miller et al., A Review of Watermarking Principles and Practices, in Digital Signal Processing in Multimedia Systems, 18, 461-85 (K. K. Parhi and T. Nishitani, Marcell Dekker, Inc., 1999), as a piece of information that is hidden directly in media content, in such a way that it is imperceptible to a human observer, but easily detected by a computer.
Although the applications of using digital watermarks differ from the applications of using paper watermarks, the underlying purpose and approach remain the same. The conventional purpose of using a digital watermark is to identify the original document, identify a legitimate document or prohibit unauthorized duplication. The approach used in applying a digital watermark is much the same as in watermarking of paper. Instead of using mesh to produce a faint indentation in the paper providing a unique identifiable mark, a digital pattern is placed into an unused area or unnoticeable area of the image, audio file or file header. Digital watermarks have also been used to send information concerning the message in which the watermark is embedded, including information for suppressing errors in signal transmission and calibration information. These conventional uses of watermarks, however, fail to fully integrate an intelligent watermark capable of supplying information along with the original signal, image or packet of data.
More specifically, prior digital watermarking techniques suffer from the shortcoming of relying on source identification being tied into the network transport protocol. Conventional source identification and authentication schemes use a source identification field embedded in a packet header by the network or transport layer for ascertaining source origin and authentication. Since network and transport layer headers get stripped off of a packet by those layers, these schemes limit identification and authentication to being performed by the data transport or network protocols.
Current fallback schemes to support the capabilities of, and to be compatible with, preexisting and deployed equipment, referred to here as legacy equipment, also inhibit the growth and deployment of new and advanced features in multimedia voice, video and data equipment. For example, in the military radio environment LPC-10e vocoders (voice operated recorder), which use linear prediction compression (LPC), have been in use for years and are widely deployed. However, performance of the LPC-10e vocoder is inadequate in severely degraded background noise environments. Newer technologies, such as in the Federal Standard MELP (mixed excitement linear processing) vocoder, have significantly reduced background noise effects. The capabilities of such newer technologies often go unused because currently deployed fallback mechanisms default to the lowest common denominator capabilities of the communicating devices. That is, these fallback schemes reduce the operating capability of the deployed equipment to the lowest capability level of the devices in communication (e.g. to the capabilities of the legacy LPC—10e vocoder). Accordingly, the advanced capabilities of new equipment goes underutilized until all legacy equipment in a network is upgraded.
Even after the legacy equipment leaves the network, the voice data streams present in the network and that were generated to be compatible with the LPC-10e vocoders remain in the legacy LPC-10e waveform even though such a waveform is not required for operation once the legacy equipment is removed from the communication network. This is due to the fact that the newer radios are not capable of discriminating new equipment sources from legacy equipment sources purely from the transport layer information in the transmitted data stream. This prevents the new equipment from automatically negotiating capabilities with other devices to operate with the greatest capabilities common to the communicating devices.